The boiling point of a working medium of a binary turbine using low-temperature exhaust heat as a heat source needs to be a low temperature. Therefore, used as the working medium is not water but freon, alternative freon, or the like having a low boiling point. However, since such a low boiling point gas is expensive, there is a demand to reduce a holding gas amount as much as possible. Here, it is thought that a falling film type evaporator used in an absorption refrigerating machine and having a high heat-exchange efficiency is adopted as the evaporator of the binary turbine (for example, PTL 1).